The present invention relates to a method of measuring damage to grain; and more particularly, it is directed to measuring the mechanical damage to grain kernels, such as corn, which occurs during harvesting, drying and handling. Although the disclosure deals specifically with corn, persons skilled in the art will readily appreciate that the method of the present invention may be applied to other grain kernels which are subject to mechanical damage during harvesting and subsequent handling operations.
Standing in the field, unhusked corn is undamaged and can last almost indefinitely in that state without diminishing its food value. Deterioration begins with the mechanical process of harvesting, and practically every subsequent operation in the drying, transporting and handling further decreases the quality of the grain. The rate of deterioration is dependent on the initial injury sustained during such mechanical processes, particularly the harvesting operation.
During harvesting, the kernels are subjected to damaging impact and compressive forces which result in breaches of the seed coat or cracks in the pericarp of the kernel. Mold may grow in the cracks or interstices of the corn kernels to such an extent that an entire shipment may be destroyed.
Currently, practically no measurements are made concerning mechanical damage of grain at the initial selling point, and no discounts are applied, therefore, for mechanical damage. Hence, there is little or no incentive for the producer of the crop to minimize mechanical damage. Rather, the incentive is to maximize the retrieval of kernels, irrespective of the final condition of the kernels. Further, there is no commercial apparatus or method available for measuring mechanical damage to corn as it is being harvested which is economical, reliable, and administered without skilled help. If such a method were available, farmers could adjust their combines to minimize the mechanical damage which would result in great savings and which could be passed on to consumers.
A number of indices or tests have been proposed for measuring mechanical damage, but these have been primarily of a theoretical or academic interest. It is believed that much of the waste due to mechanical damage could be reduced or eliminated if, for example, grain elevators or markets could establish a purchase price based, at least in part, on discounts for mechanical damage of the corn as it is delivered. This would add some incentive to the farmer who properly adjusts his combine to minimize mechanical damage.
Without a standard of measuring mechanical damage, the equipment manufacturer cannot determine when he has developed an improved harvesting machine, in the sense that it minimizes mechanical damage for a given recovery rate. Further, the farmer cannot determine when he is harvesting grain of better quality, and the grain industries cannot determine when they are processing a product of higher quality.
The U.S. Department of Agriculture has developed a numerical grading system, but it was established at a time when corn and other grains were shelled at a low moisture content, with minimal damage. Modern combines harvest a grain crop at high moisture content; and the mechanical processes used subject the kernels to substantial compressive forces which sometimes introduce substantial damage. For example, shelled corn from a combine may contain a small portion of grain fines. However, the bulk of the kernels may be seriously damaged, and the grading system mentioned above does not account for various degrees of mechanical damage.
Visual inspection has been used by research workers for accurate evaluation of mechanical damage; but this method is time-consuming and produces fatigue which influences the results.
Other tests, such as a standard germination test, an acid germination test, the tetrazolium test and a carbon dioxide production test, give good indications of mechanical damage, but take too much time to be applied, for example, at the point of purchase. Other techniques like the corn breakage tester, the electric color sorting technique and infrared photographic techniques do not give a true and accurate picture of the extent of the damage. One of the reasons for this is that some of these tests are dependent upon grain orientation or they do not respond to the depth of a breach. Other experimental methods, such as the water absorption method, the light absorption method, and a relaxation time method are not sensitive enough to distinguish the damage level between samples.
In the present invention, mechanical damage to grain is measured by taking a small sample of the grain and applying a solution of a substance which will selectively adhere only to the exposed surface of the interior of the damaged grain and not to the seed coat. Excess solution is rinsed away, and thereafter a solvent is applied which will dissolve the substance adhering to the exposed internal portion of the grain.
The amount of recovered material brought back into solution is then measured--for example, its absorbance may be measured by a spectrophotometer.
A preferred material for use in selectively adhering to the starchy area of inner portion of the grain is a dye. The mechanical damage in the sample may be represented as the total area of the kernels exposed through breach. The total amount of dye absorbed by the grain is representative of the total exposed area. Hence, the amount of dye recovered back into solution, and therefore, the concentration of the dye in the solution is representative of the mechanical grain damage. Hence, the absorbance of the solvent, as measured by a spectrophotometer or a colorimeter, is representative of the mechanical damage to the sample. The present invention thus provides a fast and efficient method for accurately determining the quality of grain. It is simple in application and does not require the use of skilled personnel. It provides statistically sound results so that it may be applied as a bulk method simply by using a sample of a large quantity of grain to be tested. The present method provides quantitative as well as qualitative results. Further, the present invention provides a damage measure which accounts for all of the various types of damage to grain, from hairline cracks and tiny spots of missing pericarp to complete breakage and fines. In other words, the entire range of damage is measured as a continuum, with the result being an overall measure of total damage.
Other features and advantages of the present invention will be apparent to persons skilled in the art from the following detailed description of a preferred embodiment accompanied by the attached drawing.